I needed to check both flatness and squareness across long surfaces and long miter fences. The most accurate tool I had was a Starrett 12” combination square. After a lot of time screwing around I came to the conclusion that the Starrett square wasn’t square and the blade wasn’t long enough to check for flatness. I borrowed my friends Woodpeckers framing square and I was done with the machine setup in no time. And it was perfectly accurate. You can see from the pic...